Rotary selector switch for microwave power sampling



Dec. 3, 1963 L. L. 0H 3, 7

ROTARY SELECTOR SWITCH FOR MICROWAVE POWER SAMPLING Filed March 9, 1961 l 20 22 E INVENTOR.

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nrramim United States Patent 3,113,276 55E ECTQR SWITCH FGR MlCllilW/aVE PGWER SaI /llPZZHNG Luis L. (ill, Seattle, Wash, sssignor to Boeing Airplane Seattle, Wash, a corporation of Delaware Filed Mar. 9, 1961, Ser. No. 94,541 3 Claims. (Cl. 333-7) This invention relates to improvements in multi-channel, high-speed microwave power sampling or monitoring devices and more particularly concerns a rotary switching device by means of which microwave field intensity, electricsl phasing and/or system power at a number of points in a microwave system may be repeatedly monitored or Otto- W1 3i utilized in a single output channel. the invention is herein illustratively described by reference to the presently preferred embodiment ther of; however, it will be recognized that certain modifications and changes therein With respect to details may be made without departing from the underlying essentials involved.

While switching devices of this invention may be con structed to operate throughout a wide range of switching frequencies, one of the important objects hereof is to accomplish switching at very high frequencies. For example, in one typical case involving 24 different channels to be monitored recurringl'y at high speed, the new switching device was operated easily at the speed of 5,809 revo lutions per minute, producing a switching freouency of 128,900 cycles per minute. While the device constitutes a mechanically driven switch, it dispenses with the requirement for mechanical contacts and thereby evercomes problems of mechanical contact wear, erosion, arcing, variations in contact resistance, etc.

Anoth r object is to provide a high speed non-contact o ally driven switching device which is superior to magnetic or lumped capacitative coupling types. For example, one device embod g this invention, developed to replace a capacitative type switchiru device, provided three times the efficiency (i.e., power transfer efliciency) with only one-fifth the weight and one-fourth the bulk, yet with twice the number of monitorable channels. Therefore, compactness, simplicity and lightness of weight represent additional obiects. Still others in clude long operating life expectancy, high efticiency, and a broad bandwidth.

The invention relies noon the principle of coupling throu h the distributed capacitances and inductances of mutual y superposed elongated transmi on line elements. One or" these comprises a relatively light-weight probe which is rotatable at high speed about a central axis and is joined to a small circular transmission line wh ch couples through a gap to a similar stationary circtuar line feeding the output 'errninal of the switch. Such a rotor is of light-weight construction and may be rotated steadily high speed to scan repeatedly a circular array of stationary line conductors comprising the coopereblc switch coupling ele ts.

The probe arm rotates in a plane which is slightly offset from a 'se cont ing the array of stationary radially disposed line conductors. The latter are anguiarly separate. on insulating supports, and with radially These and otncr features, objects and advantages of the invention will become more fully evident from the following description thereof by reference to the accompanying drawings. The terms input and output may be interchanged, of course, since the direction of energy flow is reversible through the sv 'tch.

FEGURE l is a top view of the device in its preferred form, with parts broken away.

Patented E se. 3,

FIGURE 2 is a sectional side view thereof. FIGURE 3 is a perspective view, with parts broken away to show certain other details.

As illustrated in the drawings, the switch stator con prises a flat circular metal plate in upon which are mounted a number of coaxial line fitting l4 spaced at uniform intervals about the circumference of this plate. The central conductors of these coaxial line: fittings represent the different channel inputs to the switch device. To these are connected the radially disposed elongated line conductors to supported at their inner ends by a ring 2i; of Teflon or other insulation material. These conductors 16 are spaced slightly above be flat plate ll) which serves as a ground plane for the device, lowering its input impedance. In the illustration there are twentyfour such elongated transmission line conductors 16 mounted on the supporting plate it), but obviously a different number may be provided if necessary.

Also mounted in radially disgsosed positions on the supporting plate ltl are the T-section elongated isolators or barriers 23 which project radia ly outward from sun ported einbedrncnt in the plastic ring 29 at intermediate positions between the successively adjacent line conduo tors 16. These isolators 22 are joined in conductive relationship to the plate it) at their lower edges extend upwardly slightly above the common plane of the line conductors 16. The crossbar elements of these T-section conductive isolators 2 2 add shielding effect, which would not be achieved by the more use of thin upstanding strips representing the legs of the T-section elements.

The switch rotor is driven by a motor This rotor comprises a dielectric disk 32 in which is embedded the annular transmission line conductor ring 34. The circunnerence of this ring should be less than a wavelength. Projecting radially from a point on the circumference of the ring 34 is an elongated probe arm or transmission line conductor 36. This conductor projects in parallel relationship to the plane common to the line conductors in and extends radially into overlapping relationship with those conductors. As the motor 3%} turns the arm 35 sweeps successively past the line conductors l6 and if the latter are energized a substantial portion of the energy is coupled into the conductor 36 as it passes by.

1 cover plate 33 mounted on the metal legs 12 supports the output coaxial line fitting as having a central conductor 42 which extends into contact with a point on the periphery of a circular transmission line conductor 4d similar to the conductor 34 but spaced therefrom and mounted in stationary position on the cover plate The circular line i iis also less than a full electricrd waveleng h. The outer conductor of coaxial line fitting is is connected through a ground strap to the base plate lb through the supporting leg Conductors l6 and 36 are of rod- .lte form in that they comprise straight wires or rods of the desired length and, bein" thin in a circumferential dimension of the switch, a large number of switching conductors 15 may be employed in a switch device of relatively small size.

Due to the distributed capacitance and inductance the overlapping elongated transmission line element and any or" the cooperable elements 16, ElTlCIlCllt coupling of energy from the associated input fitting 14 to the output rotary joint element is achieved. T he coupling effect is optimized by apcropriate choice or" spacing between the superposed conductors in relation to the overlapping length of these conductors. While such a device is not Ill-(l percent efficient, it need not be that efficient for purposes for which the invention is intended. Elliciencies of 70 percent are acl ievable, however, which are entirely adequate for purposes of sampling power, as in one of the applications of interest which was to sample of as the power and electrical phasing of energy at each of a large number of antennae in a linear array. Small amounts of energy are involved in terms of the power being transmitted through the switching device and it is of importance primarily that there be no phase distortion, no interference of one channel upon the sampling of an adjacent channel, and that the other objects mentioned above be attained. The presence of the isolator strips 22; between the successively adjacent stationary line conductors l6 assures a sharp and distinct cut ofi in the flow of energy from one stationary line conductor to the conductor arm 36 as the latter passes on to the next adjacent stationary line conductor, and that there is no premature coupling of energy to the conductor arm 36 from said next adjacent stationary line conductor until this cut-oil occurs. An insulating clamp and screw device 18, attached to each of the radially disposed elongated line conductors =16 at the middle section, is used to calibrate the reference power in each elongated line con ductor. The calibration is done by adjusting said insulating screw which is located under said base. Thus, when the output from the switching device, as derived through the output itting 4%, is viewed on an oscilloscope or other monitoring indicator, each of the channel signals will be separate and distinct and will be representative of the condition in the associated channel being monitorcd.

While the device has a relatively broad bandwidth (i.e., of the order of 10 percent), it may be desirable at times to change the operating frequency of a system or to use the device with a system having a considerably different operating frequency than one for which it was originally adapted. For this purpose it is merely necessary to adjust the length of the conductor arm 36 so as to vary the overlapping length of this conductor and the suc e"- sive stationary line conductors 16. This may be done by providing in the conductor 36 an expansion coupling 360, such as a telescoping joint, threaded support arm, or other equivalent means.

With the improved switching device a large number of monitoring channel fittings 14 and associated line conductons '16 may be mounted on a relatively small base, since the amount of spacing required between successively adjacent rod-like line conductors in order to achieve isolation between them is small. This is made possible by the fact that the line conductor diameters may be small and the isolating strips or T-section members 22 minimize fringing or stray field effects which would produce interference between successive monitoring positions. Moreover, because of the coupling efficiency of the device it is possible for most applications to apply the output thereof directly to a conventional oscilloscope and produce usable indications thereon without necessity of external amplification equipment.

These and other aspects of the invention will he recognized by those skilled in the art on the basis of the foregoing description of the preferred embodiment.

I claim as my invention:

1. A multichannel microwave switch comprising a conductive plate, a plurality of input connectors having first and second input conductor terminals mounted on said plate with said second input conductor terminals being electrically connected to said plate, a plurality of radially disposed conductors connected to said first input conductor terminals and insulated tron said plate, shielding means mounted between adjacent ones of said radially disposed conductors, a probe conductor mounted for rotation in coupling relationship to said radially disposed conductors, an output connector having first and second output conductor terminals, means connecting said first output conductor terminal to said probe conductor, means connecting said second output conductor terminal to said plate, and means for varying the length of said probe conductor, whereby optimum coupling may be obtained at different frequencies of operation.

2. The combination according to claim 1 wherein said means connecting said first output conductor terminal to said probe conductor comprises first and second ringshaped conductive elements mounted in spaced, coupling relationship, said first element being electrically connected to said probe conductor and said second element being electrically connected to said first output conductor terminal, whereby a rotary switch free from rotating mechanical contacts in the electrical circuit is provided.

3. The combination according to claim 1 wherein said shielding means comprises T-shaped conductive members connected to said plate.

References (Jited in the file of this patent UNITED STATES lATENTS 2,477,635 Marchand Aug. 2, H49 

1. A MULTICHANNEL MICROWAVE SWITCH COMPRISING A CONDUCTIVE PLATE, A PLURALITY OF INPUT CONNECTORS HAVING FIRST AND SECOND INPUT CONDUCTOR TERMINALS MOUNTED ON SAID PLATE WITH SAID SECOND INPUT CONDUCTOR TERMINALS BEING ELECTRICALLY CONNECTED TO SAID PLATE, A PLURALITY OF RADIALLY DISPOSED CONDUCTORS CONNECTED TO SAID FIRST INPUT CONDUCTOR TERMINALS AND INSULATED FROM SAID PLATE, SHIELDING MEANS MOUNTED BETWEEN ADJACENT ONES OF SAID RADIALLY DISPOSED CONDUCTORS, A PROBE CONDUCTOR MOUNTED FOR ROTATION IN COUPLING RELATIONSHIP TO SAID RADIALLY DISPOSED CONDUCTORS, AN OUTPUT CONNECTOR HAVING FIRST AND SECOND OUTPUT CONDUCTOR TERMINALS, MEANS CONNECTING SAID FIRST OUTPUT CONDUCTOR TERMINAL TO SAID PROBE CONDUCTOR, MEANS CONNECTING SAID SECOND OUTPUT CONDUCTOR TERMINAL TO SAID PLATE, AND MEANS FOR VARYING THE LENGTH OF SAID PROBE CONDUCTOR, WHEREBY OPTIMUM COUPLING MAY BE OBTAINED AT DIFFERENT FREQUENCIES OF OPERATION. 